In Escape The Ape, you help a small monkey called JoJo nab a rare treasure and escape from the huge gorilla that pursues him through the jungle. To do so, you draw trampolines on your device's screen and propel the little blighter further and further into the air.

Unfortunately, the air is littered with rotten bananas and other noxious articles, which should be avoided at all costs. Colliding with a hazard and plummeting towards earth results in instant death, after all.

You should, however, collect gems, which allow you to upgrade your items and improve your chances of success.

Yes, you can now play id Software's iconic first-person shooter on your iPhone, iPod touch, and iPad completely free of charge. This application features all six of the game's original episodes, meaning there are 60 levels to blast your way through.